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Reflection and shading modelsModern 3D computer graphics rely heavily on a simplified reflection model called Phong reflection model, which should not be confused with Phong shading which is an entirely different subject. In refraction of light, an important concept is the refractive index. In most 3D programming implementations, the term for this value is "index of refraction," usually abbreviated "IOR." Popular reflection rendering techniques in 3D computer graphics include: Flat shading: A technique that shades each polygon of an object based on the polygon's "normal" and the position and intensity of a light source. Gouraud shading: Invented by H. Gouraud in 1971, a fast and resource-conscious vertex shading technique used to simulate smoothly shaded surfaces. Texture mapping: A technique for simulating a large amount of surface detail by mapping images (textures) onto polygons. Phong shading: Invented by Bui Tuong Phong, used to simulate specular highlights and smooth shaded surfaces. Bump mapping: Invented by Jim Blinn, a normal-perturbation technique used to simulate wrinkled surfaces. Cel shading: A technique used to imitate the look of hand-drawn animation. 3D graphics APIs 3D graphics have become so popular, particularly in computer games, that specialized APIs (application programmer interfaces) have been created to ease the processes in all stages of computer graphics generation. These APIs have also proved vital to computer graphics hardware manufacturers, as they provide a way for programmers to access the hardware in an abstract way, while still taking advantage of the special hardware of this-or-that graphics card. These APIs for 3D computer graphics are particularly popular: OpenGL Direct3D (a subset of DirectX) RenderMan RenderWare There are also higher-level 3D scene-graph APIs which provide additional functionality on top of the lower-level rendering API. Such libraries under active development include: QSDK Quesa Java 3D NVidia Scene Graph

Scanline rendering is a rendering algorithm in 3D computer graphics that works on a point-by-point basis rather than polygon-by-polygon basis. Some point in a line is calculated, followed by successive points in the line. When the line is finished, rendering proceeds to the next line. The asset of this method is that it is not necessary to translate the coordinates of all vertices from the main memory into the working memory area each time a new polygon is encountered -- it's probable that some of the vertices have already been loaded in memory from neighboring polygons. The main memory is often very slow compared to the link between the central processing unit and cache memory, and thus avoiding re-accessing vertices in main memory can provide a substantial speed-up. This kind of algorithm can be easily integrated with the Phong reflection model and Z-buffer algorithm. Scanline rendering is used by most modern graphics cards and is typically accessed by the programmer using some 3D API such as OpenGL or Direct3D. Direct3D is part of Microsoft's DirectX API. Direct3D is only for use in Microsoft's various Windows operating systems (Windows 95 and above) and, although in a quite different version, in the Xbox. Direct3D is used to render three dimensional graphics in applications where top performance is important, such as games. Direct3D also allows applications to run fullscreen instead of embedded in a window, though they can still run in a window if programmed for that feature. Direct3D uses hardware acceleration if it is available on the graphic board. Direct3D is a 3D API. That is, it contains many commands for 3D rendering, but contains few commands for rendering 2D graphics. Microsoft continually updates Direct3D with the latest technology available on 3D graphics cards. Direct3D offers full vertex software emulation but no pixel software emulation for features not available in hardware. For example, if a program programmed using Direct3D requires pixel shaders and the graphics card on the user's computer does not support that feature, Direct3D will not emulate it. The program will most likely exit with an error message. Direct3D's main competitor is OpenGL. There are numerous features and issues that proponents for either API disagree over, see Direct3D vs. OpenGL for a summary.